The quality of wood powders depends on the size reduction technology used to produce them. The pre-drying, chipping, and conventional (impact and attritional) size reduction steps, commonly employed in industry, act to degrade wood and diminish its full potential as a renewable feedstock. In this study, the effect of using a new green (i.e. freshly harvested) milling technology, the multi-blade shaft mill (MBSM), on wood powder properties was investigated. Particle size distribution (PSD) and shape properties were measured by two-dimensional image analysis and surface area analysis was performed. The results showed that the MBSM can produce much finer powders compared to hammer milling, with particles demonstrating unique morphology and high specific surface area. Green wood milling yielded particles with the highest sphericity (0.64), aspect ratio (0.58), and micropore diameter (4.5 nm). Finer particles with spherical shapes enhanced the bulk density. Moreover, mill settings permit tailor-made powders according to the desired PSD.